This invention relates generally to an automatic transmission for a motor vehicle and more particularly to a belt drive continuously-variable speed automatic transmission for a motor vehicle. A belt drive continuously-variable speed automatic transmission comprises two variable-pitch pulleys and a belt which is V-shaped or trapezoidal in cross-section, extended between the two variable pitch pulleys. The belt drive continuously-variable speed automatic transmission is adapted to vary continuously the ratio between the rotational speeds of the shafts of the two variable pitch pulleys.
The belt drive continuously-variable speed automatic transmission is simpler in construction and smaller in size when compared with a corresponding gear transmission. However, the belt drive continuously-variable speed automatic transmission does require an additional gear mechanism for providing reverse rotation so as to be suitable for application as a transmission in a motor vehicle. Also, the belt drive continously-variable speed automatic transmission required a greater reduction ratio between the output shaft and the driving axle as compared with a gear type transmission because an increased reduction ratio is impracticable when the diameters of the pulleys must be designed within a limited range.
What is needed is a belt drive continuously-variable speed automatic transmission suitable for assembling an engine, transmission and a differential gear in an integral compact unit.